An article o a moving support surface in the form of a continuous web a sheet orapparatus for applying adhesive tape particulare self adhesive tape t

ABSTRACT

Apparatus for applying adhesive tape to a moving recipient surface in the form of a continuous web, a sheet or an article, having means for advancing the leading end of the tape into contact with the recipient surface and an applicator foot which has an arcuate working surface and secures firstly the leading end of the tape to the recipient surface and then presses successively the remainder of the tape into adhering engagement with the surface as the tape accompanies the same. The applicator foot has essentially the form of a sector of a circle, the arc of which constitutes the working surface and at the apex of which there is arrange a hub, by which the foot is journalled to a driven shaft which is in rotary engagement with the foot through an idling or free wheel movement corresponding at least to the length of the arcuate working surface of the foot.

Sept. 11, 1973 B. H. o. BERG 3,753,357

APPARATUS FOR APPLYING ADHESIVE TAPE, PARTICULARLY SELF-ADHESIVE TAPE,TO A MOVING SUPPORT SURFACE IN THE FORM OF A CONTINUOUS WEB, A SHEET ORAN ARTICLE Filed Oct. 27, 1969 3 Sheets-Sheet 1 INVENTOR. dame #060 040;515196 BY WW W p 1973 B. H. o. BERG ,758

APPARATUS FOR APPLYING ADHESIVE TAPE. PARTICULARLY q SELF-ADHESIVE TAPE,TO A MOVING SUPPORT SURFACE IN THE FORM OF A CONTINUOUS WEB, A SHEET 0RAN ARTICLE 3 Sheets-Sheet 2 Filed Oct. 27, 1969 lag- INVENTOR. 520 170600.4 0/: daze firm s.

p 1973 B. H. o. BERG ,758,367

APPARATUS FOR APPLYING ADHESIVE TAPE, PARTICULARLY SELF'ADHESIVE TAPE,TO A MOVING SUPPORT SURFACE IN THE FORM OF A CONTINUOUS WEB, A SHEET ORAN ARTICLE Filed Oct. 27, 1969 3 Sheets-Sheet 5 FIG. 3

INVENTOR. 520,? 16 060 040/6526 BY United States Patent 3,758,367APPARATUS FOR APPLYING ADHESIVE TAPE, PARTICULARLY SELF-ADHESIVE TAPE,TO A MOVING SUPPORT SURFACE IN THE FORM OF A CONTINUOUS WEB, A SHEET 0RAN ARTICLE Bror Hugo Olof Berg, Goteborg, Sweden, assiguor to MolnlyckeAB, Goteborg, Sweden Filed Oct. 27, 1969, Ser. No. 869,702 Claimspriority, application Sweden, Nov. 19, 1968, 15,72 1/ 68 Int. Cl. B32b31/20 US. Cl. 156-519 2 Claims ABSTRACT OF THE DISCLOSURE Apparatus forapplying adhesive tape to a moving recipient surface in the form of acontinuous web, a sheet or an article, having means for advancing theleading end of the tape into contact with the recipient surface and anapplicator foot which has an arcuate working surface and secures firstlythe leading end of the tape to the recipient surface and then pressessuccessively the remainder of the tape into adhering engagement with thesurface as the tape accompanies the same. The applicator foot hasessentially the form of a sector of a circle, the arc of whichconstitutes the working surface and at the apex of which there isarranged a hub, by which the foot is journalled to a driven shaft whichis in rotary engagement with the foot through an idling or free wheelmovement corresponding at least to the length of the arcuate workingsurface of the foot.

The present invention relates to an apparatus for applying adhesivetape, particularly self-adhesive tape, to a moving support surface inthe form of a continuous web, a sheet or an article.

In conventional apparatus for applying a strip of adhesive tape, a labelor the like to a support surface, the actual attachment of the tape tothe surface is normally caused by actuating a tape applicator foot witha stamping movement, thereby to press the tape, label or the likesecurely onto the surface, the tape or label being advanced to thesurface with the adhesive coated side turned downwards. In connectionwith attachment surfaces in the form of continuously moving webs, sheetsor the like, which move at a comparatively high speed, this method hasbeen found less suitable, since the stamping movement cannot be effectedat a sufficiently high frequency. Consequently, the speed of the surfacehas heretofore been adapted to the highest frequency with which the tapeapplicator foot can be actuated, which in other words means thatapplication of the adhesive tape or label has, in many instances,reduced the production rate, for example in a manufacturing line whereother working operations could otherwise have been effected at a higherrate if the speed of the moving surface had permitted it.

Apparatus are also known where the tape applicator foot comprises arotatable tape transfer drum, which rolls with its circular cylindricalsurface over the tape to be applied to the surface, but the drums ofsuch apparatus require complicated suction means, adapted to cooperatewith the rear surface of the tape, to retain the tape against the drum.Consequently, the cost of the apparatus is significantly increased andcannot, unfortunately, function at the desired high speed. Suchapparatus have therefore only found use when bonding cartons.

The object of the present invention is to eliminate the aforementioneddisadvantage and to provide a novel and improved apparatus of the typedescribed in the introduction, which permits a much higher workingfrequency and which also allows the attachment surface to move at a muchhigher speed than in those apparatus known here- 3,758,367 PatentedSept. 11, 1973 tofore for applying adhesive tapes, labels or the like tomoving surfaces. This purpose is achieved by means of an apparatusconstructed in accordance with the invention and mainly characterized inthat it includes means for advancing the leading end of the adhesivetape into contact with the moving surface; a member which is capable ofbeing urged against and exerting pressure onto said end of the tapeadvanced into contact with the surface, said member being in the form ofa rotatable applicator foot provided with an arcuate working surface andwhich by applying the end of the tape to the attachment surface firstpresses said tape fast onto said surface and then, as the tape followsthe surface, successively presses the whole of the tape fast thereto,the applicator foot substantially being in the form of a sector of acircle, the arc of which comprises the working surface of the foot andat the apex of which is arranged a hub, by means of which the foot is'journalled to a driven shaft, the foot being in rotary engagement withsaid shaft and having an idling or free wheel movement which correspondsat least to the length of said arcuate working surface.

In a particularly suitable embodiment of the apparatus of the inventionthis idling or free wheel movement can be provided for in a simple andpractical manner by arranging a gap in the hub between a dog member orsimilar movement transmitting means mounted on the shaft and an abutmentfor said dog member in the hub. In addition, in order that the dogmember and the abutment are normally held in contact with each other, atorsion spring or like element can be mounted in the hub and connectedbetween the foot and the shaft. The working surface of the applicatorfoot should have a length which corresponds to the length of the pieceof tape to be applied by the foot.

In order to ensure reliable function, the devices for advancing theleading end of the adhesive tape into contact with the moving surfaceshould include at least one driven feed roller and one holder rollerurged against said feed roller by means of, for example, a spring, theadhesive tape being passed between said rollers. If the apparatus of theinvention is primarily intended for applying pieces of tape or labels oflimited size, the feed roller or rollers should be drivenintermittently. In a particularly suitable embodiment of the apparatusof the invention the feed roller or rollers are driven for this purposevia a gearing, and the drive is provided by means of a shaft providedwith a crank web, said shaft being in turn continually driven in anarbitrary manner, for example by a pulley, a connecting rod beingarranged between the crank web and the rotatable end of a single path orfree wheel coupling, the fixed end of which is connected with the inputwheel of the gear drive. The length of the connecting rod is suitablyadjustable, to enable the feed movement to be set or adjusted.

In order to impart to the adhesive tape a small return movement in adirection opposed to the feed direction, the apparatus constructed inaccordance with the invention may be provided with a friction generatingmeans substantially comprising two coacting spring biassed clamps, saidarrangement being clamped around the stationary end of the single pathcoupling and presenting an arm which is movable between two fixedabutments in the apparatus. In this way the apparatus, through theintermediary of its arm, its stationary abutments and the frictionagainst the stationary end of the coupling is able to restrictcorotation of the input wheel in the gear drive in the idling directionof the single path coupling to a slight rearward movement of the feedroller or rollers, permitted by the movement of the arm between the twostationary abutments. As a result of this slight rearward movement, theleading end of the tape is accordingly imparted a small return movement,which avoids unnecessary contact between the tape end and a deviceintended to sever the same, said severing device suitably being mountedbetween the feed roller or rollers and the applicator foot.

The tape severing or clipping device in an apparatus constructed inaccordance with the invention is not restricted to any one particularconstruction. One device, however, which has been found particularlysimple and effective is one which presents a stationary and a pivotablecutting member, the latter cutting member being pivotally connected viaa link rod with one end of a single arm lever, which in turn ispivotally mounted at its other end and which between the ends thereofsupports a cam follower roller which lies against a cam disc mounted ona driven shaft, the movement of said disc being imparted to thepivotable cutting member as the shaft rotates via the said intermediateelements. So that the clipping or severing device may be adjusted tosome extent, the length of the link rod of said device may be madeadjustable in a known manner. Furthermore, the single arm lever on thedevice should be spring biassed against the cam disc, to ensure positiveabutment between said disc and the cam follower roller.

For the purpose of obtaining a particularly simple and robust structure,the applicator foot of an apparatus constructed in accordance with theinvention and the crank elbow and cam disc thereof may be mounted on thesame shaft, which can be driven in an arbitrary manner, for example by apulley drive system.

The apparatus of the invention will now be described in detail withreference to the appended drawings, which show one particularly suitableembodiment of the apparatus, further characterizing features of theinvention being disclosed in conjunction therewith. In the drawings FIG.1 is a side view of an apparatus constructed in accordance with theinvention, FIG. 2 is a view of said apparatus seen from the left in FIG.1, FIG. 3 is a plan view of the apparatus, and FIG. 4 shows a sectiontaken through the apparatus along the line 44 in FIG. 2.

The embodiment of the apparatus shown in the drawings is primarilyintended for applying restricted lengths of adhesive tape to a movingsurface in the form of a continuously moving web, a moving sheet or thelike. The lengths of tape, which may be in the form of adhesive labels,tape presenting coatings of adhesive on both sides thereof, with a linercoating arranged on the upper side, or the like, are passed from astorage roll, from which they are separated before being stuck to thereceiving surface. The apparatus is particularly suitable for fasteninglengths of tape to plastic diaper holders with the diapers attachedthereto, said holders being shaped, provided with diapers and adhesivetape and cut to the intended length from a rapidly moving, relativelythin, continuous plastic web.

The drawings show how the apparatus 1 of the invention is mounted forthis purpose over the moving web or recipient surface 2, which moves ona support surface 3, at least within that area of the line within whichthe apparatus is situated. The actual apparatus in the exemplaryembodiment includes a housing which is formed of two side pieces 4,between which distance pieces 5 are attached and retained by means ofbolts 6 passed through the side pieces. Between the two side pieces 4extend three shafts 7, 8, 9 which are journalled at their ends in theside pieces 4. On the first of said shafts, 7, is pivotally mounted alever 10 by means of a cylinder-shaped hub 11 arranged at one end of thelever and extending substantially over the whole length of the shaftbetween the side pieces 4. The second of the shafts 8, is the driveshaft of the apparatus, and for this purpose is rotatably journalled inthe side pieces 4 and provided with an end 12 projecting out beyond oneside pieces of the apparatus, said end 12 supporting a pulley 13 fordriving the shaft. In addition to a pulley, the shaft 8, for the purposeof driving the apparatus, may also be provided with a gear, a crank orany other suitable means for transferring a driving movement to theshaft. On the opposite end of the shaft 8, which projects beyond thesecond of the side pieces 4, is mounted an applicator foot 14, adaptedduring operation of the apparatus to fixedly apply pieces of adhesivetape to the recipient surface 2 moving on the support surface 3. Theshaft 8 presents at its centre portion situated between the two sidepieces 4 a crank web 15 and a cam plate 16. One end of a crank shaft 17is rotatably mounted on the crank web 15. The rotary movement of thedrive shaft 8 is transmitted via the crank web 15 and the crank shaft17, whose length can be adjusted in any known manner, in the form of areciprocatory movement to the elements in the apparatus which promotethe advancing movement of the adhesive tapes or labels to be applied tothe surface 2. The cam plate 16 is rigidly mounted to the drive shaft 8and serves to transmit the rotary movement thereof to a swingingmovement of the lever 10, which for this purpose supports between itstwo ends a cam follower roller 18 which is mounted between said ends andwhich constantly bears against the cam plate 16 and is urged againstsaid plate by means of a tension spring 19 or like member, which in theexemplary embodiment is mounted between the lever and a bolt 20 screwedinto a threaded hole in one side piece of the apparatus, in theproximity of the under edge thereof. The manner in which the swingingmovements of the lever 10 are utilized to drive a device for clippingthe tape advanced by the feed members will now be described. The third,9, of the shafts extending between the side pieces 4, similar to thesecond shaft 8, is mounted for rotation in the two side pieces 4. Theshaft carries a known singlepath or free wheel coupling 21, and a gear22 between the two side pieces. Both the coupling and the gear areassociated with the elements in apparatus intended for advancing thetape.

In addition to the single-path or free wheel coupling 21 and the gear22, the means for advancing the tape which is to be applied to therecipient surface 2 also includes a number of rollers 23, 24, 25, 26,supported by the front side piece, on and between which rollers theleading end 27 of the tape 29, unwound from a storage roll 28, is movedby the aforedescribed device for clipping the tape into piecs 30 ofpredetermined length to be applied to the moving surface 2 into contactwith the moving surface. Similarly to the rollers associated with thetape advancing means, the storage roll 28 is rotatably carried by thefront side piece 4, which presents a bracket 39 securely attached tosaid side piece and supporting said storage roll. The tape advancerollers, the number and arrangement of which in principle isunrestricted, are, as already disclosed in the aforegoing, in theexemplary embodiment four in number and are mounted on the outside ofand in the proximity of the under surface of the end of the side piecewhich supports the bracket 31 with the storage roll 28. Three, 23, 24,26, of the rollers are arranged in line with each other in thelongitudinal direction of the apparatus, while the remaining roller 25is arranged above the centre, 24, of the other three rollers. Theroller, 23, mounted nearest the bracket 31 is rotatably mounted on atrunnion attached to the adjacent side piece 4 and is provided with sideedges 32 which serve as a direction changing and bridle roll for thetape 29 successively unwound from the storage roll 28. The other tworollers 24 and 26 are rigidly mounted on shafts 33 and 34, respectively,rotatably mounted in the adjacent side piece and extending therethrough,the ends of said shafts 33, 34 extending into the apparatus beingrigidly connected with their respective gear 35 and 36. The gears 35 and36 engage with a further gear 37, which is rotatably mounted on atrunnion 38 attached to the inside of the respective side piece 4 andengages with a gear 22 supported by the shaft 9 extending between theside pieces 4. The said gear wheel thus forms a gear wheel for drivingthe actual feed rollers 24 and 26, the gear 22 supported by the shaft 9comprising the input gear of the gear drive. In order to obtaineffective feed of the tape 29, the tape, however, must be positivelyurged against at least one feed roller. This is achieved by the roller25 mounted above the roller 24. The roller 25 is rotatably mounted atone end of a double-arm angle lever 39, which is pivotally mounted on ashaft 40 attached to the outer side of the adjacent side piece and whichat its other end supports a traction spring 41 tensioned between anattachment on said side piece and said end, the spring causing the lever39 to bear together with the roller 25 against the tape 29 passing onthe driven feed roller 24, to act as a holder down roller and urge thetape against the feed roller and thereby ensure free advancement of thetape. The tape is advanced with its tacky surface or undersurface to beapplied to the moving surface 2 in abutment with the rollers 24 and 26and with its top surface, provided with the lining, engaging the rollers23 and 25. To reduce the surfaces of the rollers 24 and 26 Which abutthe tacky undersurface of the tape, said rollers have been provided withprojections and intermediate recesses around the circumference thereof,the depth of said recesses being such that the projections on thecircumference of the adjacent roller move in said recesses to at least apart of their height. In order to further reduce the abutting surfacesof the rollers 24 and 26, the projections extending around thecircumferences of the two rollers 24 and 26 may be given a tooth-likeconfiguration when seen from the side. By using a gear 36 with a smallnumber of teeth and the gear it is also possible to cause thecircumference of the roller 26 to move somewhat more quickly than thecircumference of the roller 24, despite the fact that the two rollerspresent the same diameter. In this way the effect is gained whereby thetape is positively prevented from adhering to the rollers 24 and 26,from which it is passed through the apparatus, clipped intopredetermined lengths 30 and advanced until the sticking side of theleading end of said tape contacts the moving recipient surface at thetape application station.

For the purpose of obtaining the feed movements of rollers 24 and 26,the free end of the connecting rod 17 is pivotally mounted to a lug 42,the other end of said rod being journalled on the crank elbow 15 of thedrive shaft 8. The lug 42 is rigidly secured to the rotatable end ofsingle-path or free wheel coupling 21 supported by the shaft 9 and theopposite, fixed end of which is rigidly connected by the gear wheel 22,which is also carried by the shaft 9. The rotary movement of the driveshaft is in this way converted to an essentially reciprocatory movementof the free end of the single path coupling, which passes idly in onedirection but, via the fixed end of the coupling, executes a carryingmovement of the gear wheel 22 in the other direction, whereby the gearwheel 22, via the intermediate gear wheels 37, 36 and 35, causes the twodriven feed rollers 24 and 26 to advance the tape 29.

To avoid the leading end 27 of the tape from adhering to the tapecutting device, a description of which is given in the following, it ispreferable to permit the tape 29 issuing from the storage roll 28 tomove back slightly, in a direction opposed to the feed direction of thetape, subse quent to a predetermined length of tape 30 having been cuttherefrom. For this purpose a device comprising substantially twocoacting clamp members 44 and 45 biassed by a spring 43 are clampedabout the fixed end of the single path coupling in a friction creatingrelationship. One of the jaws which may both be made of Bakelite orsimilar material, is provided with an outwardly projecting end in theform of an arm 46 which is movable between two stops 47 and 48, saidstops in the exemplary embodiment of the invention being in the form ofthe two limb members of a substantially U-shaped member 49 adjustablymounted by means of bolts or screws 50 and 51 in respective slots 52 and53 in the nearest adjacent side piece 4. The combined arrangement of theclamp members, the spring, the arm, the U-shaped member which presentsthe stop members, the slots and the bolts restricts, through theintermediary of its arm 46 and stops 47 and 48 and the friction createdagainst the fixed end of the single-path coupling, rotation of the gearwheel 22, carried on shaft 9, in the idling direction of the coupling 21to a smaller movement permitted by the movement of the arm between thetwo stop members, which in turn causes the feed rollers 24 and 26 torotate backwards some small amount, via the gears 35, 36 and 37,whereupon the tape 29 is forced to move slightly rearwards, in theopposite direction to the feed direction.

The aforementioned adhesive tape cutting device is mounted between thefeed rollers 24 and 26 and the applicator foot 14. In the exemplaryembodiment of the invention the device is driven by the shaft 8 via thecam plate 16, the cam follower roller 18 and the pivotal lever 10, thepivoting movement of which is transmitted to the actual cutting deviceby means of a link rod 54 pivotally attached to the free end of thelever rod 10 in a known manner so that the length of said rod can beadjusted. The cutting device comprises partly a stationary cutter 55attached to a shelf 56, which in turn is attached to the outside of theforward side piece of the apparatus and behind the feed roller 26 in thefeed direction of the tape, and partly a pivotable cutter 57 attached tothe end 59 of a pivotable double-armed lever 60 which protrudes througha slot 58 in the forward side piece 4, the opposite end 61 of said lever60 being pivotably connected to the link rod 54, which is pivotablyconnected to the free end of the lever 10. In this way the pivotablecutter, the cutting edge of which is adapted to contact the cutting edgeof the stationary cutter 55 during movement of said pivoting cutting, isthus also pivotably connected with the lever 10. For the purpose ofobtaining a stable bearing between the ends of the double-armed lever 60carrying the movable cutter 57, the lever is firmly attached to a shaft62, which is rotatably journalled on both sides of the lever in bearingblocks 63 and 64 located on the inside of the forward side piece 4.

To prevent the adhesive on the tape 29 from adhering to the cutters 55and 57, a stirrup shaped holder 65 is mounted on the outside of theforward side piece 4 in a manner to permit a filter pad 66 protrudingtherefrom to contact the pivotable cutter 57 as it moves. To these ends,the filter pad is moistened with an adhesive repelling agent, such assilicon oil, from a container 67 mounted on the top portion of theholder and the interior of which communicates in some convenient mannerwith the filter pad.

The applicator foot 14, which is attached to the end of the drive shaft8 projecting out from the front side of the apparatus, may beconstructed in a number of different ways. In the exemplary embodimentof the invention, however, the applicator foot is essentially in theform of a disc having the shape of a sector of a circle, at the apex ofwhich the foot is journalled by means of a hub 68 on the driven shaft 8,and the arc of which constitutes the working surface 69 of the foot,this surface being suitably covered with rubber or other form ofappropriate friction creating material 70 for bearing against the uppersurface of the liner coated tape. The hub 68 is rotatably mounted on theshaft 8 so as to rotate with said shaft through an idling distanceadapted to the length of the arcuate working surface 69, said idlingmovement being in the form of a gap in the hub, arranged in thedirection of rotation of the foot. This clearance is arranged between adog member 71 with which the foot is normally in rotation transmittingengagement and which is rigidly attached to the shaft 8, and an abutmentmounted in the hub 68 and coacting with the dog member 71. To ensurethat the dog member 71 on shaft 8 and the abutment in the hub 68 of theapplicator foot 14 are normally held in contact with each other, thereis provided a torsion spring 72, said spring being mounted in the huband connected between the foot 14 and the dog member attached to theshaft 8.

The particular design of the applicator foot in the exemplary embodimentof the invention provides a machine element which can be applied to andexert pressure against pieces of tape 30 cut from the length of tape 29and advanced so that their leading ends come into contact with themoving surface 2. Application of the foot 14 against the end of thepiece of tape 30 causes said end to be stuck to the moving surface,whereafter the remainder of the piece of tape is stuck fast to saidsurface as it follows with the same. The working surface 69 of theapplicator foot 14 is applied to the cut piece of tape 30 by rotatingthe foot by means of shaft 8 so that the forward end of the Workingsurface bears against the forward end of the tape, which is therebypressed against and adheres to the moving surface 2. The piece of tape30 moves at the actual speed of the recipient surface, which is slightlyhigher than the peripheral speed which the shaft 8 imparts to thearcuate working surface 69 of the foot. As a result, and because of thefriction created by the contact of the working surface with the tape 30,the applicator foot will follow the length of tape afiixed to therecipient surface 2 within the region of its idling movement in thedirection of rotation on shaft 8, whereby the working surface of saidfoot, carried by the tape, passes across the whole length of the tape 30causing the whole length of said tape to stick to the moving surface 2.The length of the working surface of the foot is approximately the sameas that of the pieces of tape which are to be fastened to the movingsurface 2, and when the whole of the tape 30 has been secured to saidrecipient surface the working surface of the foot passes out ofengagement with the tape and the friction which carries the foot at thespeed of the moving surface ceases, whereupon the foot is returned bythe torsion spring 72 in the hub 68 to the normal position of engagementwith the dog member 71 attached to the shaft 8. The foot is then onceagain moved by the shaft 8 and the dog member 71 into contact with theleading end of the following piece of tape 30 to be fastened to themoving surface 2 subsequent to it having been cut from the tape 29advanced stepwise from the storage roll 28, and so on.

When carrying out practical tests with an apparatus of the typedescribed in the aforegoing it has proven possible to stick tapes havinga length of approximately 60 mm. to a continuous plastic web atfrequencies from approximately two applications per minute toapproximately 500 applications per minute with good results. The speedof the web was thus varied from about 1 meter per minute to about 250meters per minute.

The invention is not restricted to the described and illustratedembodiment, but can be modified within the scope of the appended claims.

What I claim is:

1. In apparatus for applying adhesive tape to a moving recipientsurface, comprising means for advancing the leading end of an adhesivetape into contact with said surface, means for severing the tape to adesired length and means pressing said tape end into contact with saidsurface, said pressing means comprising an applicator foot having aWorking surface in the form of a substantially circular segment; theimprovement comprising a hub at the apex of said working surface, adriven shaft on which said hub is journalled for rotation with saidshaft in a direction such that said Working surface moves in thedirection of advance of the tape when in contact with the tape, meansinterconnecting said hub and shaft for driving said hub from said shaftwith said working surface moving at a first velocity, and meansinterconmeeting said hub and said shaft for rotation of said hubrelative to said shaft over at least the length of said working surfaceso that when said working surface presses said tape against a saidrecipient surface moving at a second "velocity greater than said firstvelocity, said tape will drive said applicator foot at a speed ofrotation greater than the speed of rotation of said shaft, whereby saidhub will rotate relative to said shaft while said working surfacecontacts said tape.

2. Apparatus as claimed in claim 1, said interconnecting meanscomprising a dog mounted on the shaft, said hub having a gap thereinterminating in an abutment engageable with said dog, and torsion springmeans acting between said foot and said shaft to urge said dog and saidabutment toward each other.

References Cited UNITED STATES PATENTS 2,333,750 11/1943 Tompkinsl56-519 2,461,860 2/ 1949 Victor 1565 19 2,467,565 4/1949 Owens et al.l56519 X 2,600,049 6/ 1952 Crider 242-99 2,794,479 6/ 1957 Granz 15 6519 2,895,534 7/1959 Steidinger 156519 SAMUEL W. ENGLE, Primary ExaminerJ. V. DORAMUS, Assistant Examiner US. Cl. X.R. 15 6552

